I would guess the following: The M3 (I think it's 2.5 mm) hex driver, the M4 (I think it's 3 mm) hex driver, and the metric hex keys from about 1.5 to 5 mm or so should cover the M2 through M6 hardware used on the M2 printer.

But an e-mail to MakerGear support should result in a response with the definitive list of tools from their Bill of Materials...